AB1686 SPECIFYING CLINICAL PHENOTYPES RELATED TO MYOSITIS ANTIBODIES
Authors: F. Schumacher, M. Kanbach, M. Berger, M. Wollsching-Strobel, S. Wigbert, D. Kroppen, S. Schwarz, W. Windisch, J. Strunk
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> The increased availability of myositis-specific-auto-antibodies (MSA) and myositis-associated auto-antibodies (MAA) represent new possibilities and challenges in everyday clinical practice for the classification of possible inflammatory rheumatic diseases (IRD). In order to achieve improved evidence regarding rare MSA and MAA and their possible significance regarding IRD other than idiopathic inflammatory myopathies (IIM), further studies are required for the classification of these new and heterogeneous disease groups. <h3>Objectives</h3> The aim of this study is a retrospective data analysis with positive MSA/MAA to analyse the significance in rheumatological clinical routine. Regarding the rather rarely autoantibodies, the occurrence and clinical association between MSA/MAA and clinical phenotypes with different disease manifestation, in this cohort should be examined. <h3>Methods</h3> A retrospective monocentric analysis of all orders to determine MSA or MAA in the period from July 2019 to May 2022 in the inpatient and outpatient sector of the Department of Rheumatology, Krankenhaus Porz am Rhein, Cologne, Germany, was carried out. A focus was placed on the following MSA and MAA: EJ, PL-7, OJ, PL-12, Mi-2, TIF1-γ, MDA5, SAE, NXP2, SRP, Ku, PM-Scl100, PM-Scl75. For each patient in whom at least one of these autoantibodies had occurred, the documented medical history was analysed retrospectively using the available files. In addition to demographic data, the existing diagnoses, documented anamnestic parameters, the various clinical examination findings and other existing diagnostic laboratory findings as well as radiological or functional examination findings has been documented at different times. <h3>Results</h3> In the defined time interval, a total of 33045 laboratory values, for the antibodies mentioned above, was ordered. A total of 238 different positive MSA/MAA were determined in 209 various patients (duplicate determinations of different autoantibodies in one patient were not excluded). The distribution of the present MSA and MAA in the various rheumatological diagnosis groups are shown in Table 1. IIM was diagnosed in 37 patients (18%) and IRD other than IIM was diagnosed in 90 patients (43%). In 82 patients (39%) no diagnosis of an IRD was made. Computed tomography of the thorax (CTtx) was performed in 92 patients. 40 examinations showed different inflammatory interstitial patterns. Of these patients, IIM was diagnosed in 14, IRD other than IMM in 19, and no IRD in 7. The number of patients with a pathological CTtx in the individual diagnosis groups is shown in Figure 1. <h3>Conclusion</h3> MSA and MAA are also positively determined in rheumatological diagnostics in patients in whom no IMM or even no IRD has been diagnosed. Nevertheless, clinical peculiarities, like changes in the CTtx can also be detected in the group of other IRDs than IMM or without IRD but with a positive status of MSA/MAA. Further investigations into specific phenotypes associated with MAA/MSA, also in the group of patients without IRD, are needed. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.